Self-winding clock



July 2, 1957 v lTARU s w I 2,797,545

' SELF-WINDING CLOCK Filed Feb.10, 1956 T 1 11 an. E

INVENTOR 4 I. ITARU OSAWA- a 2 5 Mwdiz:

ATTORNEYS United rates Pam SELF-WINDING CLOCK Itaru Osawa, Toshima-Ku, Tokyo, Japan, assignor to Kinoshita & C0., Ltd., Tokyo, Japan Application February 10, 1956, SerialNo. 564,774 3 Claims. (CI. 58-41) The present invention relates to time keeping devices such as clocks, chronometers and the like and is more particularly directed to mainspring. barrels for such devices.

The principal object of the invention is to provide a mainspring with barrel producing a constant torque for being connected to and driving a time keeping mechanlsm.

A further and important object of the invention is to provide an automatic mechanism for maintaining a mainspring tension within desired limits by keeping said mainspring wound within a restricted amount at all times.

Further objects of the invention will be in part obvious and in part pointed out in the following description of the accompanying drawings wherein,

Fig. 1 is a side elevation of the present spring barrel. n

Fig. 2 is a rear elevation of the spring barrel.

Fig. 3 is a cross sectional view of said spring barrel taken on line 3-3 of Fig. 2, and

Fig. 4 is a cross sectional view of said spring barrel taken on line 44 of Fig. 1 and its controlling members and electrical circuit.

In the drawings wherein like and corresponding ele ments are designated by similar reference characters, spring latch 2 is shown fixedly mounted on the main spring shaft 1, and the inner end is hooked onto the latch 2, while the outer end of said spring is fixedly connected to the inside of the inner barrel 4 by a rivet 5. A series of shallow curved pits 6 are pro- .vided in the outer surface of the inner barrel 4 at equal intervals therearound, in order to each receive simultaneously one of a plurality of semi-cylindrical projections 9 each provided at the inner end of one of a plurality of elastic strips 8 the outer end of which is riveted on the inner wall of the outer barrel 7, for utilizing the torque of the main-spring to rotate said barrel in the same direction as the inner barrel. There are also a plurality of adjusting screws 10 extending through and in threaded engagement with threaded openings in the wall of said outer barrel '7 each for adjusting the pressure of one of said strips 8 and its projection 9 against the periphery of the inner barrel.

On the upper part of the circumference of the outer barrel 7, there are provided a series of cuneiform notches 11 therearound to receive, one at a time, a wedge 13 of a lever 12, pivotally mounted on the pin 14 and forming part of a circuit maker and breaker of an electric circuit. A contact 15 is mounted on the other end of the lever 12 with a spring 16 fixedly fastened at one end and also fastened to lever 12 at its other end tending to pull the contact 15 into contact with a contact screw 17 only when the wedge 13 falls into one of the notches 11. A source 18 of either direct or alternating electrical current is conected to motor 19 through a circuit 20 to operate the motor 19. An end of said circuit is connected to screw 17 while an opposite end is connected to pin 14 which will conduct current therefrom to lever 12 and contact of the main spring 3 2,797,545 Patented July 2, 1957 15. A switch 21 is inserted in said circuit across the lines leading to contact 15 and contact screw 17 for closing its connection to motor 19, when said contact and contact screw are out of contact. The motor 19 is in any known manner (not shown) connected with the winding shaft 1 totransmit a rotary motion to the latter. A gear shaft 22 having a fixed gear 23 thereon is fixedly connected to the outer barrel 7 at its center by a screw 24, to be used for transmitting its rotary motion to the clock gear train (not shown).

In operation, the switch 21 is manually closed passing electrical current to the motor 19 which then begins to rotate the winding shaft 1. The spring 3 is wound thereby in the Winding direction of said spring, counter-clockwise until the spring is wound suificiently to produce a desired torque of its own then switch 21 is opened. Said wound spring then acts to rotate the inner barrel 4 in the winding direction ofthe spring. The rotation of the inner barrel 4'by the spring 3 is, however, restricted by the semi-cylindrical projections 9 entering into the pits 6.

Since each of the projections 9 is provided at one end of an elastic strip 8 and the other end thereof is riveted to the wall of said outer barrel, the inner barrel 4 rotates the outer barrel 7 in the same direction within the limits of the friction produced by the pressure of screws 10 on the elastic strips 3. Then, the gear shaft 22 and the gear 23 rotate with the revolution of said outer barrel 7, and act to transmit the rotary motion to the clock gear train.

With the continuous counter-clockwise revolution of the outer barrel 7, the wedge 13 which is sliding along the periphery of said outer barrel regularly falls into the notches 11 cut into the said outer barrel at regular intervals, and at the same time said elastic circuit is closed on the touch of the contact 15 with the contact screw 17. Thus, the motor 19 begins to turn and gives a rotary motion to the winding shaft 1 and again winds the mainspring 3. The main-spring is unwound only while the wedge 13 is sliding along the periphery of said outer barrel. The winding and unwinding of the main-spring 3 for certain intervals are thus alternately repeated.

In this connection, it is to be understood that the extent of the winding of the spring is so designed as to be a little greater than that of the unwinding. When the Winding of said main spring reaches a certain limit and increases the torque imparted to the inner barrel 4 exceeding the elastic limit of elastic strips 8, the projections 9 are caused to slip out of the pits 6. Then, the projections 9 begin to slide along the periphery of said inner barrel, and when the inner barrel rotates, by the unwinding of said main-spring, at a given torque the projections 9 again fall into pits 6, and the inner and outer barrels begin to rotate as a body. In this way, a Winding immediately after a little unwinding is continuously carried on, and when the pressure by the winding exceeds a normal torque the projections 9 slip out of the pits 6 to allow the main-spring to unwind, in consequence of which the torque of the spring is automatically kept at normal pressure.

The present invention is effectively applied to various kinds of timekeepers which require a constant torque of their main springs for securing an accuracy of operation. For this purpose, the present invention is so planned as to eliminate the difference of pressures between the beginning and end of the winding ofsaid main-spring. In some clocks hitherto used, there are types of main-spring that are operated within limits of 80% of the full pressure of the spring. But, even in such clocks, the occurrence of more or less difierences in the elasticity of the spring between the beginning and end of its winding is unavoidable, and accordingly accuracy in keeping time cannot be expected.

In short, according to the present invention, the winding and unwinding of the main-spring are alternately repeated at certain times, and when the winding of the mainspring provides a torque therefrom above a given pressure, it is unwound automatically by the slipping of the friction projections 9 of the adjusting means out of the pits 6, thus constantly kceping the torque of the mainspring within the desired limits.

I clairnz l. A constant torque spring barrel for time keeping devices comprising a main-spring, an inner barrel having said main-spring therein and connected thereto for ro tating said inner barrel, an outer barrel, friction members tending to connect said barrels for rotationtogether' up toa given torque of said main-spring, a source of electrical current, electrically operated means for winding said main-spring connected to said source of current and means operable by said outer barrel upon rotation thereof for breaking the connection of said current source with said electrically operated means.

2. A constant torque spring barrel for time keeping devices comprising a main-spring, an inner barrel having said main-spring therein and connected thereto for rotating said inner barrel, an outer barrel surrounding said inner barrel, at least one adjustable spring strip carried by said outer barrel having a projection engaging said inner barrel, said inner barrel having a series of pits for receiving said projection tending to retain said barrels for rotation together, a sourceof electrical current, electrically driven means connected to said source of current for Winding said main-spring and a switch for closing said circuit operable by said outer barrel when not rotating.

3. A constant torque spring barrel for time keeping devices as claimed in claim 2, wherein adjusting screws extend-through said outer barrel and each bears against one of said spring strips for modifying the pressure of said spring projection against said inner barrel.

References Cited in the file of this patent 5 {UNITED STATES PATENTS 

